Gunshot location systems have been used in various municipalities to assist law enforcement agencies in quickly detecting and responding to incidents of urban gunfire. The details of two such gunshot location systems are described in U.S. Pat. No. 5,973,998 to Showen et al. and U.S. Pat. No. 6,847,587 to Patterson et al., both of which are incorporated herein by reference. Showen's system locates gunshot events using a network of acoustic sensors with an average neighboring sensor separation of approximately 2000 feet. A computer receives acoustic signals from the sensors and triangulates a location, e.g., using relative time-of-arrival (TOA) information and/or angle-of-arrival (AOA) information of signals received from at least three sensors. A sensor may obtain an angle of arrival by measuring phase differences between very closely spaced microphones at the sensor site. Angles of arrival may be used to confirm a triangulated location by requiring a match between an intersection of angles and the triangulated location. Showen et al. also teach techniques for selecting a best triad of sensor signals to use in triangulation, e.g., selecting the triad that has the most number of confining events from other sensors, selecting the triad that has the most widely-spread direction vectors, selecting the triad that has the largest total signal sharpness (or impulsiveness), and selecting the triad that gives the most central location among other candidate locations from other triads.
In complex urban environments, acoustic signals often experience reflections, refraction, and complete blockage from buildings and other objects, resulting in missing or misleading signals at sensors. Additionally, short-range signals like hammering can produce confusion. Consequently, in such environments it can be difficult to triangulate gunshot locations with accuracy and confidence. There thus remains a need to provide improved gunshot location systems that meet these challenges.